The present invention concerns a centralised lubrication system for lubricating the cylinder faces in large diesel engines, particularly marine engines, including at least one lubricating apparatus with a number of reciprocating pumps actuated by cams on a rotating control shaft which is driven preferably synchronously with the main shaft of the diesel engine.
Furthermore, the present invention concerns a method for lubricating the cylinder faces in large diesel engines, particularly marine engines, including at least one lubricating apparatus with a number of reciprocating pumps actuated by cams on a rotating control shaft which is driven preferably synchronously with the main shaft of the diesel engine.
The lubricating apparatuses are traditionally designed as pump units mounted in close association with their respective cylinders, and which are connected to a supply reservoir for lubricating oil and with oil injection nozzles at different positions on the cylinder lining. Each pump unit includes a plurality of reciprocating pumps that supply oil to various lubrication points and are driven by a common rotating control shaft with cams provided thereon. By the rotation of the shaft, the cams interact with thrust heads on respective axially displacing pistons which are spring loaded in direction towards the control shaft, so that by the rotation of the shaft, the pistons will perform reciprocating movements for actuating the pistons of the reciprocating pumps.
For many years, lubricating apparatuses have operated under the operational condition that the delivery pressure from the reciprocating pumps did not have to be very high, since it is standard that the oil is to be injected in the cylinder during the upwards return stroke of the engine piston, i.e. in the course of the compression, however before the succeeding work stroke by the ignited combustion. Operation with injection or pumping pressure in the magnitude of 10 bars has thus been current.
In recent years, proposals have been made for making the lubrication more efficient by injecting the oil through atomising nozzles for achieving an oil mist lubrication during the upwards movement of the piston. Hereby the oil is, however, supplied at a far higher pressure for ensuring fine atomisation through atomising nozzles, e.g. pressures up to 100 bar or more.
In both systems, the control shaft is driven through a direct or indirect mechanical coupling with the crankshaft of the engine, whereby it becomes possible to establish power for pump actuation and simultaneously to achieve synchronisation between the engine crankshaft and the control shaft of the lubricating apparatus.
A pump unit may e.g. include a box-shaped apparatus housing carrying a row of reciprocating pumps on a wall. The unit has a valve housing with an inlet for lubricating oil, an intermediate section for accommodating a piston that protrudes into the apparatus housing and an outlet for reciprocating pump thus formed. The outlet is connected to a connector from which connecting pipes emanate to the lubrication points on the associated engine cylinder, e.g. in a number of 6-24.
The pistons are actuated for pressing in by means of actuation cams/rocker arms on a through-going control shaft which is rotated synchronously with the crankshaft of the engine. The pistons are spring biased towards the actuation cams. A set screw is provided, defining the extreme position for an associated actuation cam. The set screws may be operated for determining individual operational strokes of the pistons and thereby the associated yields of the individual reciprocating pumps.
With the mechanical coupling, there is a limitation in the possibilities of the user for controlling the injection time only for synchronised lubrication which is timed according to the rotation of the crankshaft. Furthermore, in the future it may be considered realistic that mechanical drives for the lubrication apparatus will disappear.
In some operational situations, it will be desirable to establish a non-synchronised cylinder lubrication, i.e. a cylinder lubrication which is not dependent on the rotational and angular position of the crankshaft. This is e.g. the case with pre-lubricating the cylinders, where the user has the possibility of interfering by providing a cylinder lubrication before starting the engine, and thereby before the rotation of the crankshaft has started. This is also the case for overruling a so-called slowdown where an error signal can cause reduction of the engine revolutions at a critical time, e.g. when manoeuvring in a harbour.